The present invention generally relates to motor actuated bells and, more particularly though not exclusively to motor actuated bells such as may be employed in a fire bell, an alarm bell or the like.
A typical arrangement of a conventional motor actuated bell as shown in FIG. 1, where a gong is omitted to illustrate briefly the mechanism of the bell, comprises: a motor 100 having a motor shaft 101, on which a worm gear 102 is fixedly mounted; a convertion means composed of a worm wheel 103 and a cam 105 both of which fixedly mounted on a drive shaft 104, the worm wheel 103 being mated with the worm gear 102 to transmit the rotational movement of the motor shaft 101 to the drive shaft 104 in a reduced speed; and a hammer 106 one end of which serves as a cam follower in contact with the surface of the cam 105, the other end of which strikes against an associated gong (not shown) resisting against the bias strength of a coil spring 107 to generate bell sounds.
A motor actuated bell thus constructed operates in such a manner as the motor 100 is driven to rotate the cam 105 through the meshed gears 102 and 103, and the cam 105, in turn, intermittently acts on the one end of the hammer 106 to allow the other end thereof strike against the gong. The power required to operate such a motor actuated bell is relatively large due to the need for substantial torque to enable the hammer to generate a sufficiently large sound volume, when compared with a conventional electromagnetic bell and for this reason bells of this kind are not suitable for practical use.